Add [right] alignment tag to forum BBCode and fix [centre] for new HTML guidelines

[godkama]

Needs to be tested, but should fix #12356

https://osu.ppy.sh/community/forums/topics/2117241?n=1

This also adresses the [centre] to fit new HTML guidelines:
From Mozilla Developer:

Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

[godkama]

everything should be fixed now

[godkama]

3rd times the charm amirite

[nanaya]

please take actual look at the changes

and test if it works

[godkama]

please take actual look at the changes

and test if it works

will check when I get back home

[peppy]

@godkama did you ever follow up on this?

[godkama]

@godkama did you ever follow up on this?

i did not, ended up having too much problems setting it up with wsl so now i'm gonna install linux on my machine